AP PhysicsMonday 14.04.07

HomeworkKhan AcademyMagnetism 1 & Magnetism 2

Warm UpWhat are the similarities and differences between electric potential & electric field?

Agenda1. Warm Up2. Electrostatics & Electric Circuits Test3. Homework from last 2 weeks will be

collected tomorrow.

Standards: Electrostatics & Electric Circuits

Objective: SWBAT get 60% of the points possible on the test.

Agenda1. Warm Up2. Collect HW3. Magnetic Force, particles &

wires.

Warm UpList everything you know about Magnetism and Everything you want to know about magnetism.

HomeworkKhan academy Video 3 & 4M#1

AP PhysicsTuesday 14.04.08

Standards: Objective: SWBAT understand the perpendicular relationship of magnetic field in particles and wires.

AP PhysicsWednesday 14.04.09

Agenda1. Warm Up Homework

M#2

Warm UpNA go right to the FRQ’s

Standards: Objective: Magnetostatics, charged particle through a magnetic field

SWBAT solve FRQ’s

AP PhysicsThursday 14.04.10

HomeworkM#3

Warm UpAn electron travels through a 2.7 T magnetic field pointing into the page with a speed of 2x107 m/s. Find the magnitude of the electric force acting on the electron. What direction will the electron be pushed?

Standards: D2Calculate the magnitude and direction of the force on a straight segment of current carrying wire in a uniform magnetic field.

Objective: SWBAT calculate magnetic force of a wire running through a B field & find the B field through a long wire.

Agenda1. Warm Up2. review hw3. B field through a wire4. B field of long current

carrying wire5. M#3

AP PhysicsFriday 14.04.11

HomeworkM#4-M#8

Warm UpA long wire with a radius of 20 cm has current flowing through it to the left. Draw the wire and label the magnitude and direction of the magnetic field around the wire.

Agenda1. Warm Up2. Thermodynamics Independent

Lessons3. M#4 Practice HW Due Monday

April 21st

4. Wednesday 11:00 am at the library on Tweedy AP Practice Test

Standards: D2Calculate the magnitude and direction of the force on a straight segment of current carrying wire in a uniform magnetic field. Objective: SWBAT solve current carrying wire problems

Guided Practice

An electron travels through a 2.7 T magnetic field pointing into the page with a speed of 2x107 m/s. Find the magnitude of the electric force acting on the proton. What direction will the proton be pushed?

1985B3. An electron initially moves in a horizontal direction and has a kinetic energy of 2.0 x 103 electron–volts when it is in the position shown above. It passes through a uniform electric field between two oppositely charged horizontal plates (region I) and a field–free region (region II) before eventually striking a screen at a distance of 0.08 meter from the edge of the plates. The plates are 0.04 meter long and are separated from each other by a distance of 0.02 meter. The potential differenceacross the plates is 250 volts. Gravity is negligible.

E#19 Test Review FRQ

Magnetic Forces and Fields

So far we’ve encountered 2 field Forces, Gravitation and Electric. The magnetic Force acts differently than either of the 2 previous forces.

gm

+ -

E

+ -

B

FB

. XFB

v v

g=F/m

E=F/q B=F/qv

Notice that not only does the magnetic Force act perpendicular to the magnetic field, but it only affects moving charges. If the charge isn’t moving, there is no magnetic field.

X Means i the page or towards the reader . means out of the page or away from the reader

SN

Magnetic Force on a charged Particle

F=qvB sinθ if v is not perpendicular to B.In other words you need to take the component of the velocity that is perpendicular to the magnetic field.

+

B

FB

.vθ

v_I_

+

Magnetic Field in Current Carrying Wires

-Current carrying wires are just wires with a bunch of moving electric charges (electrons) so current carrying wires have magnetic fields.

F=ILBF=(q/t)*(vt)*BF=qvB

IF

I

L

1995B7. A uniform magnetic field of magnitude B = 1.2 teslas is directed toward the bottom of the page in the –y direction, as shown above. At time t = 0, a proton p in the field is moving in the plane of the page with a speed vo = 4 x 107 meters per second in a direction 30° above the +x axis. a. Calculate the magnetic force on the proton at t = 0. b. With reference to the coordinate system shown above on the right, state the direction of the force on the proton at t = 0. c. How much work will the magnetic field do on the proton during the interval from t = 0 to t = 0.5 second? d. Describe (but do not calculate) the path of the proton in the field.

M#1

Electromagnetic Induction• Emf (E)– Electromotive force (essentially this is a Voltage

because it can drive current. • You can induce an Emf in a current loop by moving a magnet

towards or away from the current loop. • Ultimately, a changing magnetic field will induce or cause or

create electric current. • In other words, increasing or decreasing a magnetic field around

the current loop will cause electric charges to move along the wire.

• This is called Electromagnetic Induction.

Magnetic Flux

-Whenever the Strength of a Magnetic Field Changes (eg. The number of field lines increases or decreases) a current is created in a loop. -To quantify how much the magnetic field changes, we use the concept of magnetic field lines. More field lines through a loop will equal a larger magnetic flux and therefore a larger current.

-ϕ=BA cos θ where ϕ is the Magnetic Flux, B is the magnetic field and θ is the angle between the loop and the magnetic field. Units: Telsa meters squared Tm2 or Wb (weber)

Faraday’s Law

To find the Emf that is driving the induced current, you need the number of loops and the the change in Magnetic Flux through those loops. E=-NΔϕ/Δt The minus sign means that the induced emf is opposite to the change in magnetic flux. It is a reaction against the changing magnetic field.

AP Physics Thermo & Fluids Independent Unit

Thermodynamics1. 1st Law of Thermodynamics: https://www.khanacademy.org/science/physics/thermodynamics/v/first-law-of-thermodynamics--internal-energy

and/or https://www.youtube.com/watch?v=BP6sBZza1o4

for further conceptual developmenthttps://www.khanacademy.org/science/physics/thermodynamics/v/more-on-internal-energy

if this is not sufficient you can browse more Khan Academy or Miss Twu Videos2. PV Diagrams https://www.khanacademy.org/science/physics/thermodynamics/v/pv-diagrams-and-expansion-work

and https://www.khanacademy.org/science/physics/thermodynamics/v/carnot-cycle-and-carnot-enginePractice #M5Practice #M6

Fluids

1. Pressure & the Buoyant Forcehttps://www.khanacademy.org/science/physics/fluids/v/fluids--part-3

and https://www.khanacademy.org/science/physics/fluids/v/fluids--part-5

for exampleshttps://www.khanacademy.org/science/physics/fluids/v/fluids--part-6

2. Bernoulli’s Equationhttps://www.youtube.com/watch?v=PBHO7HD8GfAfor more detail see Khan academy videos 7-11 and here is a sample problemhttps://www.khanacademy.org/science/physics/fluids/v/fluids--part-12

Practice M#7

Practice M#8

M#4 Magnetic Field Through Wires C1983E3.a. Two long parallel wires that are a distance 2a apart carry equal currents I into the plane of the page as shownabove.i. Determine the resultant magnetic field intensity at the point O midway between the wires.ii. Develop an expression for the resultant magnetic field intensity at the point N. which is a vertical distance y above point O. On the diagram above indicate the direction of the resultant magnetic field at point N.

You will need to do some vector addition of the B field in this problem

M#5 1st Law of Thermo.• 1991B3 (modified) A heat engine consists of an oil-fired steam

turbine driving an electric power generator with a• power output of 120 megawatts. The thermal efficiency of the

heat engine is 40 percent.• a. Determine the time rate at which heat is supplied to the

engine.• b. If the heat of combustion of oil is 4.4 x 107 joules per

kilogram, determine the rate in kilograms per second at which oil is burned.

• c. Determine the time rate at which heat is discarded by the engine.

M#6 PV Diagrams and Carnot Cycle• 1986B5 (modified) A proposed ocean power plant will utilize the temperature difference between

surface seawater and seawater at a depth of 100 meters. Assume the surface temperature is 25° Celsius and the temperature at the 100-meter depth is 3° Celsius.

• a. What is the ideal (Carnot) efficiency of the plant?• b. If the plant generates useful energy at the rate of 100 megawatts while operating with the

efficiency found in part (a), at what rate is heat given off to the surroundings?• The diagram below represents the Carnot cycle for a simple reversible (Carnot) engine in which a

fixed amount of gas, originally at pressure po and volume Vofollows the path ABCDA.

• c. In the chart below, for each part of the cycle indicate with +, -, or 0 whether the heat transferred Q and temperature change ΔT are positive, negative, or zero, respectively. (Q is positive when heat is added to the gas, and ΔT is positive when the temperature of the gas increases.)

M#7 Buoyant Force• 2003B6.• A diver descends from a salvage ship to the ocean floor at a depth of

35 m below the surface. The density of ocean water is 1.025 x 103 kg/m3

• (a) Calculate the gauge pressure on the diver on the ocean floor.• (b) Calculate the absolute pressure on the diver on the ocean floor.• The diver finds a rectangular aluminum plate having dimensions 1.0 m

x 2.0 m x 0.03 m. A hoisting cable is lowered from the ship and the diver connects it to the plate. The density of aluminum is 2.7 x 103 kg/m3. Ignore the effects of viscosity.

• (c) Calculate the tension in the cable if it lifts the plate upward at a slow, constant velocity.

• (d) Will the tension in the hoisting cable increase, decrease, or remain the same if the plate accelerates upward at 0.05 m/s2? ____ increase ____ decrease ____ remain the same. Explain your reasoning.

M#8 Bernoulli’s Equation • B2005B5.• A large tank, 25 m in height and open at the

top, is completely filled with saltwater (density 1025 kg/m3). A small drain plug with a cross-sectional area of 4.0 x 10-5 m2 is located 5.0 m from the bottom of the tank. The plug breaks loose from the tank, and water flows from the drain.

• (a) Calculate the force exerted by the water on the plug before the plug breaks free.

• (b) Calculate the speed of the water as it leaves the hole in the side of the tank.

• (c) Calculate the volume flow rate of the water from the hole.